Electronic vent valve

ABSTRACT

An electronic vent valve for an electronically controlled pneumatic (ECP”) braking system having a plurality of braking sites at which a braking force can be applied. The ECP braking system includes a master controller processing circuit, individual braking control units located proximate each of the braking sites and a brake pipe supplying compressed air to the braking sites. The electronic vent valve is in fluid communication with the compressed air carried by the brake pipe and has an open position for substantially venting the compressed air from the brake pipe and a closed position for substantially retaining the compressed air within the brake pipe. The electronic vent valve includes a control circuit for causing the valve to open during emergency braking operations, thereby assuring a rapid decrease in the brake pipe pressure. The control circuit preferably includes a brake pipe pressure sensor and a microprocessor for calculating a rate of change of the brake pipe pressure (dP/dt) and for causing the valve to open whenever the calculated rate of change of brake pipe pressure exceeds a threshold value. The control circuit can additionally cause the valve to open in response to a direct command from the master controller and can transmit to the master controller various operational characteristics of the braking system and the microprocessor itself.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application is directed to similar subject matter asis disclosed in U.S. patent application Ser. No. 09/044,352 filed onMar. 19, 1998 by Angel P. Bezos and entitled “Improved AAR CompliantElectronic Braking System” and in U.S. patent application No. ______filed on ______ by Robert C. Kull and entitled “Locomotive to ECP BrakeConversion System”. The subject matter disclosed in the abovecross-referenced copending U.S. patent applications is hereby expresslyincorporated by reference with the same effect as if fully set forthherein.

FIELD OF THE INVENTION

[0002] The present invention relates, in general, to pneumatic brakingsystems such as are typically employed on rail transport vehicles (e.g.,trains) and other relatively large wheeled transport vehicles (e.g.,heavy trucks). More particularly, the present invention relates to aso-called “electronically controlled pneumatic” (hereinafter “ECP”) typeof braking system for such vehicles, most particularly ECP brakingsystems for trains and other rail transport vehicles.

BACKGROUND OF THE INVENTION

[0003] The principles of a pneumatic braking system are well understoodby those of ordinary skill in the relevant art. Typically, an onboardair compressor furnishes and replenishes as necessary compressed air tothe system. A so-called “main reservoir” is typically employed tomaintain a substantially constant feed pressure to the system downstreamthereof. The main reservoir is recharged by the onboard compressorwhenever its pressure drops below a predetermined level.

[0004] A train “consist” is formed of a number of related railcarslinked end to end. The main reservoir, normally located in a forwardlocomotive along with the compressor, feeds a pneumatic line, commonlyreferred to as a “brake pipe” which typically extends the length of thetrain In the formation of a train consist, the individual brake pipesections located on each individual railcar are linked together throughpneumatic couplings. On each individual railcar, a “branch pipe”supplies compressed air from the brake pipe running the length of thetrain to the individual braking components of the individual railcar,which typically include a so-called “AB-Type control valve” (alsosometimes referred to as a “triple valve”), an “auxiliary reservoir”, an“emergency reservoir” and the brake cylinders of the railcar. [Examplesof AB-Type control valves are the ABD, ABDX and ABDW control valvescurrently or previously manufactured by Westinghouse Air Brake Company,i.e., “WABCO”.] During times when the brakes are “released” (e.g., nobraking force being applied), compressed air from the pneumatic brakepipe is supplied via the branch line to maintain a predeterminedcompressed air charge within the auxiliary and emergency reservoirs ofeach railcar in the train consist. In some designs, a so-called“combined auxiliary and emergency reservoir” is provided on a railcar.The brakes on an individual railcar are applied by supplying compressedair from at least the auxiliary/emergency reservoir(s) located on therailcar to the brake cylinders of the railcar. The compressed airdisplaces the pistons of the brake cylinders to apply a mechanicalbraking force to the wheels of the railcar.

[0005] In the conventional pneumatic braking system, as originallydeveloped, the only means for actuating the transfer of compressed airfrom the auxiliary/emergency reservoir(s) to the brake cylinders isthrough the brake pipe itself. An engineer or other operator lowers thebrake pipe pressure, e.g., by manipulating a brake lever on a brakecontrol panel located in the locomotive. For example, the brake pipepressure can be lowered by venting the brake pipe to atmosphere inresponse to movement of a control handle by the engineer.

[0006] The AB-Type control valves located on each individual railcar areconstructed such that they respond to a lowered brake pipe pressure bysupplying compressed air from at least the auxiliary reservoir locatedon each railcar to the brake cylinders of the railcar, thereby applyingthe brakes of the railcar. The amount of air pressure supplied from theauxiliary reservoir to the brake cylinders by the AB-Type control valvesis proportional to the amount by which the brake pipe pressure islowered by the engineer. Typically, the control handle allows theengineer to apply a continuously variable braking force beginning with aso-called “release” position (in which the brake pipe pressure is at amaximum and the braking pressure applied at the individual railcars istherefore at a minimum, e.g., the brakes are released), through a“minimum service” brake application, a “full service” brake applicationand ultimately to an “emergency” brake application (in which the brakepipe pressure is at a minimum and the braking pressure applied at theindividual railcars is therefore at a maximum). Other brakingapplications may be available to the engineer such as suppression andcontinuous service, but the principle is basically the same, namely,that the engineer's movement of the braking control handle lowers thebrake pipe pressure, and the AB-Type control valves located in theindividual railcars respond by supplying air from theauxiliary/emergency reservoir(s) located on the individual railcars tothe brake cylinders proportionately according to the degree by which thebrake pipe pressure is lowered by the engineer.

[0007] When the engineer moves the control handle to the “emergency”position, the brake pipe pressure is precipitously reduced. As is wellunderstood in the art, the individual AB-Type control valves on theindividual railcars are constructed such that, when the brake pipepressure drops below a determined pressure, the AB-Type control valvestransfer compressed air from both the auxiliary and emergency reservoirson each railcar to the brake cylinders of the railcar, resulting in agreater mechanical braking force being applied than in a service brakingapplication, wherein only compressed air from the auxiliary reservoirsis supplied to the brake cylinders.

[0008] One advantage of the above-described conventional pneumaticbraking system is that it provides a “fail safe” mechanism. Since thebrakes at the individual railcars are applied in response to a decreasein brake pipe pressure, a rupture of the brake pipe, a failure of thecompressor, etc. results in the brakes being applied and not in a brakefailure. In view of the dire consequences of brake failure on a railwaytrain, it is understandable that pneumatic braking development has beencharacterized by the fail safe concept.

[0009] However, a limitation of such a conventional pneumatic brakingsystem described above that has been long appreciated is the delay inbraking that occurs as the change in brake pipe pressure propagatesalong the length of a train. For example, it has been estimated that abrake pipe pressure drop in a freight train of approximately one mile inlength may take about one minute to travel the length of the train if itis a service brake application and about one-half minute if it is anemergency brake application.

[0010] To overcome this limitation, so-called “electronically controlledpneumatic” (or “ECP”) braking systems have been developed. ECP brakingsystems also utilize the concept of control valves Located on eachrailcar which transfer previously stored compressed air fromauxiliary/emergency reservoir(s) located on the railcars to the brakecylinders thereof to generate a braking force. However, in an ECPbraking system, the control valves can be electrically actuated (i.e.,through electropneumatic valves). Therefore, signals to the railcarcontrol valves are transmitted at least electrically, rather than onlythrough the brake pipe pressure, thereby substantially eliminating thepropagation delay along a long freight train mentioned above.

[0011] In a typical implementation of an ECP braking system on a freighttrain, the lead locomotive is provided with a master controller (e.g.,microprocessor controlled) which receives input data signals describingthe degree of braking application applied by the engineer via the brakecontrol handle. The master controller then formulates braking commandsfor the railcars and sends electrical braking command signals toindividual car control units or “CCU”s (e.g., also microprocessorcontrolled) located on each individual railcar which describe the degreeof braking to be applied by each individual railcar. The electricalbraking command signals sent by the master controller typically describethe braking application in terms of a percentage of the pressurerequired for a full service brake application, for example, with 0%indicating a release of brakes, 15% indicating a minimum service brakeapplication, 100% indicating a full service brake application and 120%indicating an emergency brake application.

[0012] The communication signals between the master controller and theindividual CCU's are typically conveyed by an electrical communicationline (e.g., an “electrical trainline”) which runs from railcar torailcar throughout the length of the train. Like the pneumatic brakepipe, the electrical trainline consists of a sequential series ofindividual segments which are joined end to end during the formation ofa train consist.

[0013] In order to provide for a redundant or fail safe manner ofoperation, the pneumatic braking system is frequently retained on trainshaving an ECP braking system implementation. For example, the ECPelectrical trainline may be employed to communicate both service andemergency braking applications to the individual railcars, while thepneumatic brake pipe may be employed to communicate only backupemergency braking applications to the individual railcars.

[0014] As noted above, during an emergency braking operation, the brakepipe pressure is dropped as rapidly as possible, since it is theseverely reduced brake pipe pressure which initiates the transfer ofcompressed air from both the auxiliary and emergency reservoirs to thebrake cylinders. However, on long trains, particularly long freighttrains, brake pipe pressure changes, even an emergency brake pipepressure reduction, can take up to one-half minute to propagate thelength of the train.

[0015] The present invention is directed to producing a very rapid dropin the brake pipe pressure upon the detection of conditions indicatingthat an emergency brake application has been initiated. The presentinvention is particularly adapted to use in conjunction with an ECP typeof braking system. However, the present invention could also be used inconjunction with the conventional type of pneumatic braking systemdescribed above.

OBJECTS OF THE INVENTION

[0016] One object of the present invention is the provision of anelectronic vent valve for attachment to the brake pipe of anelectronically controlled pneumatic braking system for quickly andprecipitously lowering the brake pipe pressure in response to a receivedelectrical signal indicating the initiation of an emergency brakingcondition, thereby ensuring that the control valve of the pneumaticbraking system will respond to the rapidly lowered brake pipe pressureby supplying an appropriate compressed air charge from the onboardauxiliary/emergency reservoirs to the brake cylinders so as to initiatethe desired emergency braking action.

[0017] Another object of the present invention is the provision of suchan electronic vent valve which is additionally capable of monitoring theexisting brake pipe pressure and opening the vent valve in response to anegative rate of change in the brake pipe pressure (dP/dt) that exceedsa threshold rate of pressure change determined to be indicative, in andof itself, of an emergency braking condition.

[0018] A further object of the present invention is the provision ofsuch an electronic vent valve which can, upon determining the existenceof an emergency braking condition, perform optional emergencysubroutines, such as, for example, determining subsequent rates ofchange of brake pipe pressure (dP/dt) and reporting such rates of changeof brake pipe pressure to a master controller unit, actuatingappropriate warning indicators, attempting to reactuate the vent, etc.

[0019] A still further object of the present invention is the provisionof such an electronic vent valve which is capable of performing periodictest subroutines to determine whether it is in proper operationalcondition.

[0020] A yet further object of the present invention is the provision ofsuch an electronic vent valve that is reliable in operation andefficient in manufacture.

[0021] In addition to the objects and advantages of the presentinvention described above, various other objects and advantages of theinvention will become more readily apparent to those persons skilled inthe relevant art from the following more detailed description of theinvention, particularly when such description is taken in conjunctionwith the attached drawing Figures and with the appended claims.

SUMMARY OF THE INVENTION

[0022] In one aspect, the invention generally features an electronicallycontrolled vent valve for a pneumatic brake system, the pneumatic brakesystem including a brake pipe carrying compressed air, theelectronically controlled vent valve including a valve for connecting tothe brake pipe and for being in fluid communication with the compressedair carried by the brake pipe, the valve having an open position forsubstantially venting the compressed air from the brake pipe and aclosed position for substantially retaining the compressed air withinthe brake pipe, an electrically operated actuator for moving the valvebetween the open position and the closed position and a control circuitfor controlling the electrically operated actuator to move the valvebetween the open position and the closed position.

[0023] In another aspect, the invention generally features anelectronically controlled vent valve for an electronically controlledpneumatic braking system, the electronically controlled pneumaticbraking system having a plurality of braking sites at which a brakingforce can be applied, the electronically controlled pneumatic brakingsystem including a master controller processing circuit for generatingand supplying electrical braking command signals and an individualbraking control unit located proximate each of the plurality of brakingsites for receiving the electrical braking command signals generated andtransmitted by the master controller processing circuit, theelectronically controlled pneumatic braking system further including abrake pipe supplying compressed air to the plurality of braking sites,the electronically controlled vent valve including a valve housing forconnecting to the brake pipe and for receiving the compressed air fromthe brake pipe, a valve member disposed within the valve housing, thevalve member having an open position for substantially venting thecompressed air from the valve housing and a closed position forsubstantially retaining the compressed air within the valve housing, anelectrically operated actuation mechanism for moving the valve memberbetween the open and closed positions and an electronic control circuitfor controlling the electrically operated actuation mechanism to therebycause the valve member to move between the open and closed positions.

[0024] The present invention will now be described by way of aparticularly preferred embodiment, reference being made to the variousFigures of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a cross-sectional elevational view of an electronic ventvalve, constructed according to the present invention.

[0026]FIG. 2 is a flow chart showing a first embodiment of analgorithmic procedure implemented by a microprocessor component of theelectronic vent valve of FIG. 1.

[0027]FIG. 3 is a flow chart showing a second embodiment of analgorithmic procedure implemented by a microprocessor component of theelectronic vent valve of FIG. 1.

[0028]FIG. 4 is a flow chart showing a third embodiment of analgorithmic procedure implemented by a microprocessor component of theelectronic vent valve of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Prior to proceeding to a much more detailed description of thepresent invention, it should be noted that identical components whichhave identical functions have been identified with identical referencenumerals throughout the several views illustrated in the drawing Figuresfor the sake of clarity and understanding of the invention.

[0030] Referring now to FIG. 1, an electronic vent valve constructedaccording to the present invention and designated by reference numeral10 generally includes a valve 12, an electrically operated actuator 14for moving the valve 12 between an open position and a closed positionand a control circuit 16 for controlling the electrically operatedactuator 14 so as to cause the electrically operated actuator 14 to movethe valve 12 between the open and closed position in accordance withalgorithmic procedures described more fully below. The valve 12 isitself contained within a valve housing 18 which has an internal cavity20 within which is positioned a valve member 22. The valve housing 18 isprovided with a preferably threaded female connection 24 for connectingto a threaded male fitting of a brake pipe of a pneumatic brakingsystem. Preferably, the threaded connection 24 is a 1 and ¼ inch pipethread connection. Due to such connection of the valve housing 18 to thebrake pipe of the pneumatic braking system, the internal cavity 20 ismaintained at substantially the brake pipe pressure.

[0031] The valve housing 18 is additionally provided with a vent orifice26 that opens to the surrounding ambient atmosphere. Preferably, thevent orifice 26 is fitted with a vent protector 28 which has a hornportion 30 and a screen 32 for excluding insects and preventing debrisfrom clogging the vent orifice 26. The vent protector 28 is preferablyconnected to the valve housing 18 via another threaded connection 34.

[0032] The valve member 22 includes a generally disk shaped valveportion 36 and a valve stem 38 extending therefrom. The generally diskshaped valve portion 36 is preferably provided with an raised annulus 39which surrounds the vent orifice 26. An annular flange 40 extendsradially from the valve stem 38 and slidingly contacts a bore 42provided in the valve housing 18 opposite the vent orifice 26 such thatthe valve member 22 is free to slidingly reciprocate within the bore 42thereby closing and opening the valve 12 by respectively blocking andunblocking the vent orifice 26. To maintain a pressure seal within theinternal cavity 20, the annular flange 40 is provided with a peripheralgroove 44. A resilient O-ring 46 is positioned within the peripheralgroove 44. The valve 12 is biased by a preferably coiled spring member48 towards a normally closed position shown in FIG. 1, wherein theraised annulus 39 of the generally disk shaped valve portion 36 is incontact with the interior wall of the internal cavity 20, therebysurrounding and effectively closing the vent opening 26.

[0033] The electrically operated actuator 14 for moving the valve 12between the open and closed positions is preferably provided in the formof a solenoid 50 having a coil 52 and an armature 54 extending throughthe coil 52. The armature 54 is axially connected so as to extend thevalve stem 38, for example, by a threaded connection 56. As is wellknown, energization of the coil 52 causes a movement of the armature 54towards the center of the coil 52 and thus an upward movement (as viewedin FIG. 1) of the valve member 22 against the downward biasing force ofthe coil spring 48, thereby opening the vent orifice 26 to the ambientatmosphere.

[0034] The solenoid 50 can be selectively energized by the controlcircuit 16 which preferably includes a microprocessor 58 controlling asolid state relay driver 60. The solid state relay driver 60 receiveselectrical power to energize the solenoid 50 from positive and negativepower connections 62 which are typically connected to the aforementionedelectrical trainline which runs from railcar to railcar over the lengthof the train. Typically, such an electrical trainline will include a 74volt direct current power supply line. The solid state relay driver 60selectively energizes the solenoid coil 52 as directed by themicroprocessor 58 through electrical leads 64. The microprocessor 58itself is also connected to the electrical trainline by a communicationport 66 through which the microprocessor 58 receives data from thepreviously mentioned master controller typically located in the leadlocomotive. Preferably, the communication port is an RS422 communicationport well known in the microprocessor arts.

[0035] The valve housing 18 is further provided with another orifice 66to which there is affixed a pressure transducer 68, such pressuretransducers being well known in the electronic arts. The pressuretransducer 68 may be digitally implemented or may alternatively besupplied as an analog pressure transducer coupled with an analog todigital converter so as to provide digital signals indicative of thepressure within the internal cavity 20 of the housing 18 which, as notedabove, is the brake pipe pressure. Repeated digital signals from thepressure transducer 68 indicative of the brake pipe pressure aretransmitted to the microprocessor 58 through at least a pair of signalleads 70 (e.g., signal and ground).

[0036] It will be appreciated that the electronic vent valve 10 asdescribed above can be selectively opened to ambient atmosphere throughactuation of the solenoid 50 by the microprocessor 58 and that themicroprocessor 58 can on a repetitively updated basis monitor thepressure within the interior chamber 20, i.e., the brake pipe pressure.We now turn to a more detailed description of the algorithmic proceduresimplemented in the functioning of the microprocessor 58 and illustratedin FIGS. 2-4.

[0037]FIG. 2 illustrates a first embodiment of algorithmic proceduresimplemented in the microprocessor 58. This first embodiment has two mainbranches 80 and 82, depending upon whether or not an emergency brakesignal has been received by the microprocessor 58 (e.g., through theelectrical trainline) from the master controller located in thelocomotive. If, at decision point 84, an emergency brake signal has beenreceived from the locomotive, then in branch 80 the microprocessor 58(in FIG. 1) actuates the solenoid 50 to immediately move the valve 12 tothe open position, thereby causing a rapid decrease in the brake pipepressure. As noted above, the AB-Type control valves located on eachrailcar react to a precipitous drop in the brake pipe pressure bytransferring compressed air from both the auxiliary and emergencyreservoirs to the brake cylinders. The microprocessor 58 additionallyreports the occurrence of the vent actuation to the locomotive via theRS422 communications port 66.

[0038] If, at decision point 84 an emergency brake signal has not beenreceived from the locomotive, then in branch 82 the microprocessor 58reads the current brake pipe pressure via the pressure transducer 68,computes the rate of change with respect to time of the brake pipepressure dP/dt and determines whether the computed rate of change ofpressure dP/dt is greater than or equal to a threshold valuedP/dt(Emergency). If the threshold is met or exceeded, the valve 12 isagain immediately moved to the open position to rapidly drop the brakepipe pressure.

[0039] Regardless of whether the valve 12 has been opened, during eachiteration the microprocessor 58 typically reports at 86 to the mastercontroller various operational characteristics such as, for example, thecurrent pressure being read by the pressure transducer 68 and the mostrecently computed rate of change of brake pipe pressure dP/dt, as wellas any other desired operational characteristics of the microprocessor58 itself. The operational characteristics reported at 86 need not bereported immediately to the master controller, but can be saved in aregister to be reported to the master controller in response to apolling operation periodically conducted by the master controller, if sodesired.

[0040]FIG. 3 illustrates a second embodiment of algorithmic procedureswhich may be implemented in the microprocessor 58. In addition to thetwo branches 80 and 82 shown in FIG. 2, the algorithm of FIG. 3 containsan optional emergency subroutine 88, which may be incorporated to refinethe procedures carried out whenever the valve 12 has been opened due toan emergency braking condition having been determined. The emergencybraking condition may have been commanded by the master controller viathe RS422 communication port 66 or the emergency braking condition mayhave been independently initiated by the microprocessor 58 itself due tothe calculated dP/dt having exceeded the determined threshold value.

[0041] During the optional emergency subroutine 88, the microprocessor58 determines whether the valve 12 has in fact opened after themicroprocessor 58 has actuated the solenoid 50 to cause an opening ofthe valve 12. For example, by repeatedly reading the pressure transducer68 the microprocessor 58 can determine whether the pressure within theinterior cavity 20 of the housing 18 is falling sufficiently rapidly toindicate that the valve 12 has in fact been actuated to the openposition. As part of such a check, the microprocessor 58 can calculatedP/dt to determine if the rate of change of the brake pipe pressure issufficiently great to indicate that the valve 12 has actually opened.Additionally, the microprocessor 58 can report back to the mastercontroller via the RS422 communications port 66 whether the valve 12 hasin fact opened and can actuate an audible and/or visible warning in thelocomotive if the valve 12 has failed to open properly. Still further,the microprocessor 58 can attempt to reopen the valve 12. Variousoptional emergency measures may be taken as appropriate.

[0042]FIG. 4 illustrates a third embodiment of algorithmic procedureswhich may be implemented in the microprocessor 58. In the embodiment ofFIG. 3, the two main branches 80 and 82 of FIGS. 2 and 3 are shown,together with the optional emergency subroutine 88 of FIG. 3.Additionally, FIG. 4 shows how an optional periodic test subroutine 90can be incorporated into the inventive algorithm. In the optionalperiodic test subroutine 90, a periodic timing function 92, which maybe, for example, a hardware or software implemented register, determineswhen a periodic operational test of the electronic vent valve is to beconducted at 94. The periodic test conducted at 94 may be, for example,any of a number of self-testing/self-diagnostic subroutines performed bythe microprocessor 58 which are well known and understood by those ofordinary skill in the microprocessor arts. For example, one suchself-testing subroutine which may be performed by the microprocessor 58is a testing for proper functioning of the random access memory (RAM)associated with the microprocessor 58.

[0043] While the present invention has been described by way of adetailed description of a number of particularly preferred embodiments,it will be apparent to those of ordinary skill in the art that varioussubstitutions of equivalents may be affected without departing from thespirit or scope of the invention as set forth in the appended claims.

I claim:
 1. An electronically controlled vent valve for a pneumatic brake system, such pneumatic brake system including a brake pipe carrying compressed air, said electronically controlled vent valve comprising: a valve for connecting to such brake pipe and for being in fluid communication with such compressed air carried by such brake pipe; said valve having an open position for substantially venting such compressed air from such brake pipe and a closed position for substantially retaining such compressed air within such brake pipe; an electrically operated actuator for moving said valve between said open position and said closed position; and control means for controlling said electrically operated actuator to move said valve between said open position and said closed position.
 2. An electronically controlled vent valve for a pneumatic brake system, according to claim 1, wherein such pneumatic brake system further includes a master controller processing circuit for generating electrical braking command signals and wherein: said control means includes means for moving said valve between said open position and said closed position in response to such electrical braking command signals generated by such master controller processing circuit.
 3. An electronically controlled vent valve for a pneumatic brake system, according to claim 1, wherein said control means includes: a brake pipe pressure sensor for sensing a pressure of such compressed air in such brake pipe and for generating brake pipe pressure signals indicative of such pressure of such compressed air in such brake pipe; and a processor for receiving said brake pipe pressure signals and for controlling said electrically operated actuator to move said valve between said open position and said closed position dependent upon said brake pipe pressure signals generated by said brake pipe pressure sensor.
 4. An electronically controlled vent valve for a pneumatic brake system, according to claim 3, wherein: said processor includes emergency pressure monitoring means for calculating a rate of change of said brake pipe pressure signals generated by said brake pipe pressure sensor and for controlling said electrically operated actuator to move said valve to said open position when said calculated rate of change of said brake pipe pressure signals exceeds a threshold value.
 5. An electronically controlled vent valve for a pneumatic brake system, according to claim 4, wherein such pneumatic braking system includes a master controller processing circuit for processing brake signal commands and wherein: said control means additionally includes a communication circuit for receiving data from and for transmitting data to such master controller processing circuit of such pneumatic brake system.
 6. An electronically controlled vent valve for a pneumatic brake system, according to claim 5, wherein: said control means additionally includes direct vent actuation means for controlling said electrically operated actuator to move said valve to said open position in response to a signal received through said communication circuit from such master controller processing circuit of such pneumatic brake system.
 7. An electronically controlled vent valve for a pneumatic brake system, according to claim 5, wherein: said processor additionally includes reporting means for transmitting to such master controller processing circuit of such pneumatic brake system through said communication circuit at least one of: a signal representing actuation of said vent by said electrically operated actuator; a signal representing said brake pipe pressure signals; and a signal representing said calculated rate of change of said brake pipe pressure signals.
 8. An electronically controlled vent valve for a pneumatic brake system, according to claim 5, wherein: said control means additionally includes means for transmitting to such master controller processing circuit of such pneumatic braking system over said communication circuit at least one operational characteristic of said control means.
 9. An electronically controlled vent valve for a pneumatic brake system, according to claim 3, wherein said processor additionally includes emergency subroutine means for performing at least one of the following actions: a) actuating at least one of an audible signal and a visible signal; b) controlling said electrically operated actuator to move said valve to said open position.
 10. An electronically controlled vent valve for a pneumatic brake system, according to claim 3, wherein: said processor includes means for testing actuation of said vent by said electrically operated actuator.
 11. An electronically controlled vent valve for a pneumatic brake system, according to claim 3, wherein said processor includes at least one microprocessor circuit.
 12. An electronically controlled vent valve for a pneumatic brake system, according to claim 1, wherein said electrically operated actuator includes a solenoid for moving said valve between said open position and said closed position and a relay driver, said relay driver being operable to drive said solenoid in accordance with signals generated by said control means.
 13. An electronically controlled vent valve for a pneumatic brake system, according to claim 11, wherein said at least one microprocessor circuit includes periodic test means for performing a periodic self test of the operational status of said at least one microprocessor circuit.
 14. An electronically controlled vent valve for an electronically controlled pneumatic braking system, such electronically controlled pneumatic braking system having a plurality of braking sites at which a braking force can be applied, such electronically controlled pneumatic braking system including a master controller processing circuit for generating and supplying electrical braking command signals and an individual braking control unit located proximate each of such plurality of braking sites for receiving such electrical braking command signals generated and transmitted by such master controller processing circuit, such electronically controlled pneumatic braking system further including a brake pipe supplying compressed air to such plurality of braking sites, said electronically controlled vent valve comprising: a valve housing for connecting to such brake pipe and for receiving such compressed air from such brake pipe; a valve member disposed within said valve housing; said valve member having an open position for substantially venting such compressed air from said valve housing and a closed position for substantially retaining such compressed air within said valve housing; electrically operated actuation means for moving said valve member between said open and closed positions; and an electronic control circuit for controlling said electrically operated actuation means to thereby cause said valve member to move between said open and closed positions.
 15. An electronically controlled vent valve for an electronically controlled pneumatic braking system, according to claim 14, wherein said electronic control circuit includes: brake pipe pressure sensor means for sensing a brake pipe pressure existing in such brake pipe and for generating brake pipe pressure signals indicative of such brake pipe pressure existing in such brake pipe; and means for causing said electrically operated actuation means to move said valve member between said open and closed positions dependent upon said brake pipe pressure signals generated by said brake pipe pressure sensor means.
 16. An electronically controlled vent valve for an electronically controlled pneumatic braking system, according to claim 15, wherein: said electronic control circuit includes a microprocessor; said microprocessor being supplied with brake pipe pressure signals from said pressure sensor means; and said microprocessor includes emergency pressure monitoring means for monitoring a rate of change of said brake pipe pressure signals and for causing said electrically operated actuation means to move said valve member to said open position when said rate of change of said brake pipe pressure monitored by said microprocessor is beyond a threshold value.
 17. An electronically controlled vent valve for an electronically controlled pneumatic braking system, according to claim 16: wherein said electronically controlled vent valve additionally comprises electrical communication means for communicating electrical braking signals between said microprocessor and such master controller processing circuit of such electronically controlled pneumatic braking system.
 18. An electronically controlled vent valve for a pneumatic brake system, according to claim 17, wherein said electronic control circuit additionally includes direct vent actuation means for causing said electrically operated actuation means to move said valve member to said open position in response to an electrical braking command signal generated by and received from said master controller processing circuit through said electrical communication means.
 19. An electronically controlled vent valve for a pneumatic brake system, according to claim 17, wherein said microprocessor further includes reporting means for transmitting to such master controller processing circuit of such electronically controlled pneumatic brake system through said electrical communication means at least one of: a signal representing movement of said valve member to said open position by said electrically operated actuation means; a signal representing said brake pipe pressure signals; a signal representing said monitored rate of change of said brake pipe pressure signals; and a signal representing an operational characteristic of said microprocessor.
 20. An electronically controlled vent valve for a pneumatic brake system, according to claim 16, wherein said emergency pressure monitoring means further includes means for actuating at least one of an audible signal and a visible signal. 